The ladder diagram consists of multiple rungs, each coil can form a rung, each rung represents a logic equation, and each rung has multiple branches.
In the ladder diagram, relays, contacts, and coils are not physical entities, but bits stored in PLC registers. I just sorted out an information package and put it at the end of the video.
When programming, the normally open/normally closed contact can be referenced infinitely, but the coil output can only be performed once.
The flow in the ladder diagram is a "conceptual current" that can only flow from left to right.
The operation of the user program is based on the contents of the PLC input/output image register, and the result of the logic operation can be used by the subsequent program immediately. Relevant information has been organized to the end of the video.
The internal relay of PLC can only store the intermediate state of logic control, and cannot be used for control.
The output coil cannot directly drive the on-site actuators, but needs to be driven by the power device on the I/module.
The basic logic instructions of PLC are mainly based on bit logic operations. In the bit logic instruction, unless otherwise specified, the valid area of the operand is: I, Q, M, SM, T, C, V, S, L, and the data type is BOOL. Contact and coil instructions are divided into standard instructions, immediate instructions, negation instructions, and positive (negative) jump instructions.
It just so happens that I have plc information here. If you need it, you can private me.